[Python-Dev] Add transform() and untranform() methods (original) (raw)

Victor Stinner victor.stinner at gmail.com
Thu Nov 14 23:40:41 CET 2013

Oh, I forgot to mention that I sent this email in reaction to this issue:

http://bugs.python.org/issue19585

Modifying the critical PyFrameObject because the codecs API raises surprising errors doesn't sound correct. I prefer to fix how codecs are used, than modifying the PyFrameObject.

For more information, see the issue #7475 which a long history (4 years) and many messages. Martin von Loewis wrote "I would still be opposed to such a change, and I think it needs a PEP." and I still agree with him on this point. Because they are different opinions and no consensus, a PEP is required to explain why we took this decision and list rejected alternatives.

http://bugs.python.org/issue7475

Victor

2013/11/14 Victor Stinner <victor.stinner at gmail.com>:

Hi,

I saw that Nick Coghlan documented codecs.encode() and codecs.decode(), and changed the exception raised when codecs like rot13 are used on bytes.decode() and str.encode(). I don't like the functions codecs.encode() and codecs.decode() because the type of the result depends on the encoding (second parameter). We try to avoid this in Python. I would prefer to split the registry of codecs to have 3 registries: - "encoding" (a better name can found): encode str=>bytes, decode bytes=>str - bytes: encode bytes=>bytes, decode bytes=>bytes - str: encode str=>str, decode str=>str And add transform() and untransform() methods to bytes and str types. In practice, it might be same codecs registry for all codecs just with a new attribute. Examples: - utf8: encoding - zlib: bytes - rot13: str The result type of bytes.transform/untransform would be bytes, and the result type of str.transform/untransform would be str. I don't know which exception should be raised when a codec is used in the wrong method. LookupError? TypeError "codec xxx cannot be used with method xxx.xx"? Something else? codecs.encode/decode() documentation should be removed. The functions should be kept, just in case if someone uses them. Victor

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